Gregor
Mendel is usually considered to be the founder
of modern genetics. Though farmers had
known for centuries that crossbreeding of animals
and plants could favor certain desirable traits,
Mendel's pea plant experiments conducted
between 1856 and 1863 established many of the rules
of heredity.

An Augustinian monk living in what is now the
Czech Republic, Mendel had access to an
experimental garden in which he could breed true lines
of pea plants and patiently wait for
them to crossbreed in specified combinations.
He worked with seven characteristics of pea
plants: plant height, pod shape and color, seed
shape and color, and flower position and color.
Using the example of seed color, his results showed that when a yellow pea and a green pea were bred together their offspring plant was always yellow. However, in the next generation
of
plants, the green peas reappeared at a ratio
of 1:3.

To explain this phenomenon, Mendel coined
the terms recessive and dominant in
reference
to certain traits. (In the preceding example,
green peas are recessive and yellow peas are
dominant.) He published his work in 1866, demonstrating the actions of invisible “factors”—what we now call genes —in providing
for visible traits in predictable ways.

Mendel never
enjoyed recognition in his lifetime. In fact,
it was more than three decades later, in
1900, that three scientists doing agricultural
research discovered his 1866 paper. Erich
Tschermak, Hugo de Vries, and Carl Correns independently
verified several of Mendel's
experimental findings, and the "age of genetics" was born.
In
the next several decades, scientists would learn
more about genes and the special substance
called DNA
that carried each living thing's
specific traits.